This invention relates generally to air purifiers and, more particularly, to a portable room air purifier providing filter use information.
There is an ever increasing need to provide clean air environments both at home and in the work place. Especially in urban areas where pollutant levels are in excess of those recommended for good health, it is necessary to upgrade living and work environments by removing harmful contaminants from the air.
Airborne pollutants contribute to respiratory infections and illnesses and can be especially damaging to individuals with respiratory problems including allergies or from Asthma. Symptoms of high pollutant levels are burning eyes, nose and throat irritations, headaches, dizziness, coughing and sneezing. Individuals are constantly inhaling particles of dust, smoke, pollen, mold spores, acids, bacteria, viruses, animal hair, soot, and harmful chemicals.
In an effort to provide some relief from airborne pollutants, many offices and homes utilize central filtering systems to remove particles from the air. Unfortunately, such centralized systems, which are economically available, do not remove more than approximately 80-85% of the particles in the air and are only effective on particles which are approximately one micron or larger.
The need to have substantially purified air has resulted in the creation of special filter elements which are defined as HEPA filters. HEPA stands for High Efficiency Particulate Air filters which, by federal standard, are filters with a minimum efficiency of 99.9%. The industry defines HEPA filters as those filters which are efficient in removing 99.97% of airborne particles of a size of 0.3 microns or larger.
Although such HEPA filter elements were originally designed for use in ultra clean environments including laboratories, electronic and biological clean rooms, and hospitals and the like, such filters have been used in portable structures which may be utilized in individual room environments. U.S. Pat. Nos. 5,435,817 and 6,036,757 each disclose such a portable room air purifier having a housing in which a filter element is positioned so as to be intermediate an air inlet and an air outlet and wherein a fan is driven by a motor so as to urge air inwardly through the inlet and discharge the air towards the outlet. The portable room air purifier further includes at least one scroll oriented so as to direct air from the fan generally tangentially with respect to the axis of the fan through a scroll discharge opening. A deflector is mounted in spaced relationship with respect to the discharge opening. The deflector tapers inwardly relative to the scroll to thereby define an open passageway through which air is directed as it is exhausted through the air outlet. The disclosed filter structure provides improved uniform filtered air distribution with a relatively compact device. However, one problem associated with prior HEPA air purifiers is the creation of somewhat undesirable noise levels.
The object of this invention, therefore, is to provide an improved air cleaner which produces lower levels of ambient noise.
The invention is a portable air cleaner including a housing defining an air inlet, an air outlet, and an air flow path therebetween, a centrifugal blower retained within the air flow path and operable to draw air through the inlet and a filter retained within the housing and disposed to transmit air circulating in the air flow path out of the outlet. Also included is a conveyor surrounding the blower and defining a scroll shaped passage having one end disposed to receive air from the blower and an opposite end disposed to discharge air into the filter, the conveyor being shaped and arranged to obstruct all rectilinear paths between the blower and the opposite end. The absence of unobstructed paths between the blower and the opposite end significantly reduces the noise level produced by the air cleaner.
According to one feature of the invention, the filter is a cylindrical filter axially displaced from the blower and the conveyor, an inner wall surface of the filter and the housing defines a chamber communicating with a substantially circular opposite end, and a portion of the air flow path extends between an outer wall surface of the filter and the air outlet. Noise abatement is enhanced further by this structural arrangement.
According to another feature of the invention, the conveyor includes a ramp surface partially defining the passage and arranged to convey air between the one end and opposite ends in a direction having a component axial to the centrifugal blower. These structural features provide cyclonic expansion of air at the outlet to further reduce sound output.
According to still other features of the invention, the filter is mounted above the conveyor and blower, the housing includes a portable shell having top, bottom and side walls, the air inlet is a first annular grillwork defined in a lower portion of the side wall, and the air outlet is a second annular grillwork defined in an upper portion of the side wall. These structural features provide desirable, low noise air flow between the inlet and outlet.
According to an additional feature of the invention, sound reducing material is disposed axially between the blower and a bottom surface of the shell. Further noise reduction is obtained by use of the sound reducing material.